Powder Coating Adhesion Testing

A. Hi David, although everything is in the end somewhat subjective I suppose, if instead of just going for the general gist of cross-hatch testing you very carefully do standardized tests like ASTM D3359 tape test, with rollers per FED-STD-141, following the specs to the letter, I think the results will be reasonably repeatable and meaningful.
Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. Accurate test method: If you're using the right specified tape, cross-hatch cuts, procedures as per your adhesion testing standard used and the same as the pencil hardness test. Your tests should be as accurate as it should be. But you can include more severe tests like Mandrel bending, impact, pressure cook or permeability (done on sample plates), sawing and milling (on sample product) to reinforce your quality systems (ISO test methods). Dubious results may warrant adhesion failure of your product.

A. GM9071P describes Tape Adhesion for Paint Finishes. I realize that is not your exact application, but it better describes the tape than the ASTM method.

A. As with most people trying to obtain results using the "tape test", my frustration was with the variation in the method more so than the tape. The ASTM D3359 has an appendix that highlights some of the "Procedural Problems", such as the method of application of the tape and the angle it is removed. While searching the ASTM website for this standard I found links to companies that have made equipment that take that variation out of the test. It's interesting to know a problem that has been around for a long time has only recently been solved. I've done thousands of these tape tests now and can probably offer some decent advice on how to make them more consistent from operator to operator and from time to time. Thank you.

A. GM 9071P mentions 3M 610, 3M 670, or 3M 898.

A. Read ISO 2409 cross-cut test, then you will find answer! YES! IF boiling water cross-cut test passed, most of test of powder coating will pass too!

----
Ed. note: Please see also topic 46657, "Process/Procedure for Cross Hatch Test - Measuring Adhesion by Tape Test" and topic 13961, "Strength of a powder coated part"